![]() ![]() These trends imply a factor of 100 increase in the extent of seafloor anoxia and suggest the presence of a shallow oxygen minimum zone (OMZ) that inhibited the recovery of benthic animal diversity and marine ecosystem function. ![]() We observe abrupt decreases in and δ 238U across the end-Permian extinction horizon, from ∼3 ppm and −0.15‰ to ∼0.3 ppm and −0.77‰, followed by a gradual return to preextinction values over the subsequent 5 million years. Here we use paired records of uranium concentrations () and 238U/ 235U isotopic compositions (δ 238U) of Upper Permian−Upper Triassic marine limestones from China and Turkey to quantify variations in global seafloor redox conditions. However, the extent and duration of Early Triassic anoxia remains poorly constrained. Delayed Earth system recovery following the end-Permian mass extinction is often attributed to severe ocean anoxia. ![]()
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